Individuals diagnosed with Attention Deficit Hyperactivity Disorder (ADHD) smoke more than the general population, initiate use at a younger age, and in general report more difficulty trying to quit. Despite alarmingly high rates of smoking among this clinical population, little experimental work has been done to investigate possible mechanisms underlying this comorbidity. The overall goal of this application is to characterize smoking and smoking withdrawal in individuals with and without ADHD who are nicotine dependent. Eighty dependent individuals will be recruited and assigned to one of two groups (N=40 each). One of the groups will be free from any psychiatric diagnosis except nicotine dependence. The other group will be diagnosed with ADHD. We will initially characterize baseline smoking behavior across the ADHD and non-ADHD groups. Then, we will investigate the extent to which a contingency management approach is successful at facilitating abstinence and occasioning withdrawal across these two groups. Finally, we will carefully assess the patterns of withdrawal and relapse across the two groups. This project will be the first to systematically characterize smoking and smoking withdrawal in ADHD and non- ADHD smokers using rigorous laboratory techniques. The results of this project will lead to subsequent grant applications to further explore basic neuropharmacological mechanisms associated with ADHD and smoking risk. Data generated will also lead to subsequent clinical projects to develop more effective interventions for nicotine dependence in this high risk group. This project will be the first to systematically characterize smoking and smoking withdrawal in ADHD and non-ADHD smokers using rigorous laboratory techniques. The results of this project will lead to subsequent grant applications to further explore basic neuropharmacological mechanisms associated with ADHD and smoking risk. Data generated will also lead to subsequent clinical projects to develop more effective interventions for nicotine dependence in this high risk group. [unreadable] [unreadable] [unreadable]